Good things first. Got a brand new 3T Time Capsule running in the background, my MBA 2011 never was faster and smoother and by having to recover the hard drive I got rid of lots of unnecessary applications and files that just amassed over time. The bad? Always told myself and friends to never ever upgrade to a first OS version. Did it the for first time and guess it was the final option whether I want to enable FileVault option that screwed up the whole process. Got an error message, then a strange stuck gray screen I've never seen before Luckily a local Apple guy could somehow recover my data, backed it up and got me a clean Mavericks reinstall. The moral of the story? I'm anal about maintaining a healthy computer. Didn't help with OS 10.10. Next time Apple advertises yet again the best and newest and fastest and whatever OS, I will, like in the past, just wait for version x.1 or even x.2. In case you're about to try 10.10, most people have no problems I assume. If you're one of the few running into a worst case scenario, just have that backup.